Motor control apparatus



Malh 19, 1953 J. W. WALLACE MOTOR CONTROL APPARATUS Filed Oct. Vl5, 1959lNvENToR John W. Wallace ATTORNEY WITNESSES QA fg# 5,081,654 MOTORCONTROL AHARATUS .lohn W. Wallace, Bulialo, NSY., assigner toWestinghouse Electric Corporation, East Pittsburgh, Pa., a corporationof Pennsylvania Fitted Oct. 15,1959, Ser. No. Site d laims. (Cl. Sil-56) The present invention relates in general to automatic motor controlapparatus for a machine device or the like, and more specificallyrelates to automatic motor control apparatus for a strip rolling millwherein the thickness of the roll strip is measured and any errorrelative to a desired strip thickness results in an error signal that isemployed to automatically control the operation of a motor operativewith `the rolling mill.

It is an object of the present invention to provide improved motorcontrol apparatus for controlling the operation of a machine device,such as for example a metallic strip rolling mill.

It is another object to provide improved motor control apparatus forbetter controlling the operation of a metallic strip rolling millregarding strip thickness error as a function of the length of thatstrip.

It is a different object of the present invention to provide improvedmotor control apparatus operative with a strip rolling mill or the likefor better controlling an operational error condition in accordance witha predetermined timing program.

It is a still different object of the present invention to provideimproved motor control apparatus operative with a strip rolling mill forbetter controlling an operational error condition of that rolling mill,and more particularly to better sense the magnitude of any operationalerror condition and to time the error correction in accordance with themovement of the strip through the rolling mill.

It is an additional object to provide improved motor control apparatusoperative with a machine device for sensing an operational error of thatmachine device and to better control the operation of that machinedevice regarding the elimination of such operation error.

It is a still additional object to provide improved motor controlapparatus operative with a machine device and in accordance with anoperational error to better control the operation of that machine deviceregarding the correction or elimination of any such `operational erroras determined by thc error sensing position and relative to the machinedevice operation.

These and other objects and advantages of the present invention willbecome still more apparent from a study of the following descriptiontaken in conjunction with the drawing which shows a schematic view ofthe motor control apparatus in accordance with the present invention.

ln FIGURE l there is shown a strip rolling mill l including an upperroller 12 and a lower roller 14, operative with a continuous strip ofmetallic material i6, a screw down motor lli is operative to adiust thespacing between the upper roller l2 and the lower roller 14 and therebyto control the thickness of the strip 16 leaving the mill stand itl. AnX-ray thickness measuring gauge Ztl or the like device is operative toprovide an error signal in accordance with the difference between theactual thickness or the strip 16 and a predetermined desired orreference thickness. The operation of the thickness measurement gauge2li in this regard is well known to persons skilled in this particularart.

The error signal supplied by the thickness gauge Ztl is applied to afirst signal sensing device 22 which is operative to provide an outputsignal only when the error signal reaches a predetermined magnitude orvalue such htates Patent O1 ice as 1% of the maximum error signal thatis provided tby the thickness gauge Ztl. A second signal sensing device24- is responsive to the error signal from the thickness gauge 2li andis operative to provide an output signal only when the error signalreaches a greater predetermined magnitude or value such as a 2%thickness error. A third signal sensing device 26 is responsive to theerror signal from the thickness gauge 2t) and is operative to provide anoutput signal only when the error signal reaches a third and greaterpredetermined magnitude or value, for example a 5% error. A polaritysensing device 28 is operative with the error signal from the thicknessgauge 2l) to provide a first output signal to an output terminal 30 whenthe error signal indicates that the actual strip thickness is greaterthan the desired or reference strip thickness. The polarity sensingdevice 28 is operative to provide a second output signal to a secondoutput terminal 32 when the error signal indicates that the actual stripthickness is less than the desired or reference strip thickness. Theoutput signal from the signal magnitude sensing device 22 energizes anON input of a memory logic device 34.

The memory logic device per se is well known to persons skilled in thisparticular art and is operative such that when its ON input receives aninput signal, a rst output terminal 36 is not energized with a unitvalue output signal and the second output terminal 38 is so energized.When the OFF input terminal of the memory device 34 is energized by aninput control signal, the output terminal 36 receives the unit valueoutput signal and the output terminal 3s is not energized or receives azero value output signal. The memory device 34 is a binary type deviceproviding at each of its output terminals either a unit value outputsignal or a zero value output signal.

When the magnitude sensing device 22 senses a 1% error signal from thethickness gauge 20 it provides an output signal to the ON terminal ofthe memory device fil-i which in turn terminates a unit value outputsignal previously provided to the terminal 36 which is connected to theinput of a first timer device 49. The timer device 4% is operative toprovide no output signal or a zero value output signal for as long as acontrol input of that timer device is energized by an input signal, andthen for a predetermined time period only it provides a unit valueoutput signal after which time period it again provides the zero valueoutput signal. This type of timer device -is per se well known topersons skilled in this particular art. This timer device also has alockout input which is operative to hold oi its unit value output signalfor as long as a lockout signal is applied to its lockout input.

A well known timing relay will operate in this manner, for example. Itmay have a set of contacts that ,are picked up and held open for as longas its control winding is energized by either an input control signal oran input lockout signal. When neither of these input signals areprovided, after a predetermined time period that can be determined by acharged capacitor the contacts close and the timing relay provides anoutput signal through those closed contacts. The output of the tirsttimer device is connected to one input terminal of each of a first NORlogic device i2 and a second NOR logic device 44.

lt should be noted that a NOR logic device per se is well known topersons skilled in this particular art and is operative to provide aunit value output signal only when all of its input terminals aresimultaneously not energized by a unit value input signal.

The output of the magnitude sensing device 24 is connected to the ONinput terminal of a memory device 46 which is shown as the upper inputterminal and that memory device 46 in turn is connected to energize asecond timer device 48 having its output connected to an input of eachof the NOR logic devices 42 and 44. The signal magnitude sensing device26 is connected to energize the ON input of a memory device Si) that inturn is connected to energize an input of a third timer device 52 havingan output connected to one input of each of the NOR logic devices 42 and44.

The signal polarity sensing device 28 has its output terminal 30connected to the ON input of a memory device 54 having a first outputterminal 56 connected to energize an input of the NOR logic device 42and a second output terminal 58 connected to energize an input of theNOR logic device 44. The output terminal 32 of the signal polaritysensing device 28 is connected to energize the ON input of the memorydevice 60 having a first output terminal 62 connected to energize aninput of the NOR logic device 44 and a second output terminal 64connected to energize an input of the NOR logic device 42.

The NOR logic device 42 is connected to control the operation of a DOWNrelay 66 having contactors con-f nected in ,a motor control circuit withthe screw motor 18 and a direct current voltage source 68 such that whenthe DOWN relay 66 is energized, its contactors cause the screw motor 18to operate in a direction to decrease the spacing between the upperroller 12 and lower roller 14 of the rolling mill 10. The NOR logicdevice 44 is operative with an UP relay device 70 having contactsoperative between the D.C. voltage source 68 and the screw motor 18 suchthat when the UP relay device 78 is energized, the screw motor 18 iscaused to move in a direction to increase the spacing between the upperroller 12 and the lower roller 14 of the rolling mill 10. The latteroperation is believed to be readily apparent from the illustrated motorcontrol circuit.

A mill motor 72 is connected to drive the rolling mill and in additionis connected to a pulse source 74 such that the output pulses from thepulse source 74 have a frequency proportional to the operating speed ofthe rolling mill 18, and therefore the movement of the strip 16. Theoutput pulses from the pulse source V74 are connected to an input of aNOR logic device 76, a second input of the same NOR logic device isconnected to be energized by an output terminal 78 of a memory device 80having an ON input connected to be energized by a voltage source 82through a relay device 84 having a contactor connected between thevoltage source 82 and the ON input terminal of the memory device 80. Therelay device 84 is connected in the armature circuit of the screw motor18 such that when each of the DOWN relay device 66 and the UP relaydevice 76 are not-energized, and the screw motor 18 is generating oroperating in a dynamic braking circuit arrangement, the lresultingcurrent flow through a dynamic braking resistor 86 will provide avoltage' drop across the dynamic braking resistor 86 to cause the relaydevice 84 to be energized. After the screw motor 18 has stopped itsdynamic braking operation such that the screw motor 18 has effectivelystopped its motion, the relay device 84 becomes deenergized todisconnect the voltage source 82 from the ON input of the memory device8i). A conductor 87 is directly connected between the voltage source 82through the contacter of the relay device 84 to a third input :of theNOR logic element 76 for a purpose as will be later described.

The output of the NOR logic element 76 is connected to .an input of apulse counter device 88 which is operative to count a predeterminednumber of applied input pulses and thereafter provide a single outputpulse through an output terminal 90 which is connected to the OFF inputof each of the memory devices 34, 46, 50, 54 and 68 and further isconnected through a conductor 92 to the OFF input of the memory device80.

In the operation of the motor control apparatus as shown in the drawing,the output pulse or signal from the pulse counter device 88 is operativeto cause each of the memory devices 34, 46, Si), 54, 6G and 80 to bereset and operative in its OFF condition such that an output signal issupplied by each of the memory devices 34, 46 and 5t) to the respectivetimer devices 40, 48 and 52. Therefore, each of the timer device doesnot supply a control signal to each of the NOR logic devices 42 and 44.However, an output signal is supplied by the memory device 88 throughits upper output terminal 78 to an input of the NOR logic device '76,which is operative as a gating device relative to output pulses from thepulse source 74. When the output signal from the upper output terminal78 is applied to an input of the NOR logic device 76, this blocks orprevents the output pulses from the pulse source 74 from reaching theinput of the pulse counter device 88.

The same output signal from the pulse counter device S8 is operative toset the memory devices 54 and 60 in their OFF condition of operationsuch that the memory device 54 supplies a unit value output signalthrough its terminal S6 to an input of the NOR logic device 42 andsupplies a zero value output signal through its output terminal 58 to aninput of the NOR logic device 44, thereby preventing the NOR logicdevice 42 from providing an output signal. On the other hand, the memorydevice 6i) provides a unit value output signal through its output-terminal 62 to the NOR logic device 44 and provides a zero Value outputsignal through its terminal 64 to an input of the NOR logic device 42,thereby preventing the NOR logic device 44 from providing an outputsignal.

With the mill motor 72 in operation and the strip 16 moving through therolling mill 1t?, any error present in the strip thickness is sensed bythe thickness gauge 20 and is supplied to the signal lmagnitude sensingdevices 22, 24 and 26 and to the signal polarity sensing device 28.Assume for the purpose of example that the strip thickness error isbetween l and 2%, such that only the signal magnitude sensing device 22responds to the error signal and the signal magnitude sensing devices 24and 26 do not respond to the error signal. In addition, assume forpurposes of illustration that the strip thickness error is such that theactual strip thickness is greater than the desired or reference stripthickness, such that the signal polarity sensing device 28 is operativeto provide an output signal through its output terminal 30 to the upperor ON input of the memory device 54. The output signal from the signalmagnitude sensing device 22 causes the memory device 34 to operate inits ON condition to thereby no longer energize an input of the firsttimer device 40. The timer device 40 will now provide a unit valueoutput signal to each of the NOR logic devices 42 and 44 after a firstpredetermined time period, such as for example one second. The outputsignal from the signal polarity sensing device 28 through its outputterminal 3i) causes the memory device 54 to operate in its ON conditionof operation such that the output terminal 56 now receives a zero valuecontrol signal which it applies to an input of the NOR logic device 42,and the output terminal 58 now receives a one value output signal whichit applies to an input of the NOR logic device 44.

Until the one value control signal from the first timer device 40 isprovided at the end of the one second timing period and simultaneouslythe one value control signal from the memory device 54 is also notprovided the NOR 'logic device 42 now is able to provide an outputsignal to the DOWN relay device 66 in that all of its inputs are now notenergized by one value control signals or in other energized With zerovalue control signals. This causes the contacts of the relay device 66to energize for the one second time period the screw motor 18 in adirection to decrease the spacing between the upper roller 12 and thelower roller 14 of the rolling mill 10.

After the desired error correction period, which in the present assumedillustration is a time period of one second, the one value controlsignal from the first timer device 40 appears to an input of each of theNOR logic devices 42 and 44 to thereby terminate the energization of therelay device 66 and to cause it to return to its position as shown inthe drawing. This completes a dynamic braking circuit between the screwmotor 18, armature and the dynamic braking resistor 86 which results inthe energization of the dynamic braking resistor S6 until the screwmotor 18 stops its operation. The relay device 84 is operated by theresulting voltage drop across the dynamic braking resistor 86 to causethe voltage source 82 now to energize the ON input of the memory device80 to cause the latter memory device 80 to become operative in its ONcondition of operation such that the one value output signal is nolonger supplied through the terminal 78 to an input of the NOR logicdevice 76. The voltage source 82 is connected through the conductor 86to a third input of the NOR logic device 76 to effectively prevent itfrom ypassing the output pulses from the pulse source 74 to the pulsecounter device S8. After the screw motor 18 has stopped its motion dueto the effect of the dynamic braking action, the relay device 84 againbecomes deenergized to disconnect the voltage source 82 from the thirdinput to the NOR logic device 76, such that the output pulses from thepulse source 7 4 now are applied to the pulse counter device 88.

After a predetermined number of pulses, for example, six pulses havebeen counted by the pulse counter device, which six pulses correspondsubstantially to the transport time delay of a given portion of thestrip 16 passing from the rolling mill 10 to the thickness gauge 20 andsuch that the thickness error corrective action can be measured by thethickness gauge 20, an output pulse is supplied by the pulse counterdevice to the OFF input of the memory device 8G through the conductor 92which causes the memory device 80 to return to its OFF condition ofoperation and to again provide an output one value signal through itsterminal 78 to lan input of the NOR logic device 76 to thereby preventadditional pulses from the pulse source 74 from being applied to thepulse counter device 8S. This same output pulse from the pulse counterdevice 88 is operative to reset the pulse counter device S8 as wellknown to persons skilled in this particular art. This same output pulseis further operative to reset each of the memory devices 34, 46, 5t), 54and 60. The control input of the iirst timer device is now againenergized by the memory device 34, the second and third timer devicesrespectively 48 and 52 continue to be energized by their respectivememory devices 46 and 5d. The memory device 54 is returned to its OFFcondition of operation such that the output terminal 56 provides a unitvalue control signal to the NOR logic device 42 and the output terminal58 provides a zero value control signal to the NOR logic device 44. Thememory device 69 remains in its OFF condition of operation with theoutput terminal 62 providing a unit value control signal to the NORlogic device i4 and the output terminal 64 providing a zero valuecontrol signal to the NOR logic device 42.

Thusly, it will be seen that the error signal caused the DOWN relaydevice 66 to be energized for a time period which varies in length inaccordance with the magnitude of the error signal provided by thethickness gauge 26x in the illustration, the error signal was operativeto provide only a one second energization of the screw motor 18, howeverit the error signal had been between 2 and 5% the second timer device 48would have been operative to provide a greater error correction period,for example a two second correction period. The lockout signalconnection from the lower output terminal 47 of the memory device 46 tothe lockout input of the tiret timer device 49 is operative to preventan output signal from the timer device d0 when the memory device 46 isoperative in its ON condition of operation. Similarl'j/,the lockoutsignal connection from the lower output terminal 51 of the memory deviceSi) to a lockout input of each of the timer devices 40 and 4d isoperative to prevent an output signal from each of the timer devices ditand 4S when the memory device 5t) is operating in its ON condition ofoperation. Ii the error signal from the thickness gauge 20 had beenabove 5%, the signal magnitude sensing device 26 would have caused thethird timer device 52 to energize the DOWN relay device 66 for a iivesecond time period. In this regard it should be noted that the iirsttimer device 40 and the second timer device 48 have their lockout inputsrespectively energized by any unit value signal from the `memory device50, output terminal 51 as provided when that memory device 50 isoperative in its ON condition of operation, such that only the largertive second time period provided by the third timer device 52 iscontrolling.

The polarity of the error signal corresponding to the actual stripthickness being one of greater or smaller than the desired or referencestrip thickness is operative with the polarity sensing device 28 tocause one or the other of the relay devices 66 and 76 to be operative.ln the provided illustration, the DOWN relay device d6 was energized inthat the error signal corresponded to an actual strip thickness greaterthan the desired or reference strip thickness. After the screw motor 18is energized for the desired predetermined time period, it is stopped bya dyn-amic braking vcircuit which in turn is operative to block theoutput pulses from the pulse source 74 until after the screw motor i8stops its movement. Then the signal pulses from the pulse source 74 andcorresponding to the movement of the strip 16 as sensed through theoperation of the rolling mill and the mill motor 72 are applied to apulse counter device for again resetting the control apparatus shown inthe drawing.

Thusly, the system as shown in the drawings is operated by a thicknesserror signal which is supplied to a group of signal comparators orsignal magnitude sensing devices7 each of which responds to a differentmagnitude ot1 error signal, and the direction of the error signal issensed When one of the voltage comparators responds to the error signal,it controls its particular timing circuit such that the screws arejogged or energized for a given length of time in a direction determinedby the polarity or direction of the thickness error. When the joggingoperation is completed, a pulse counter is energized by signal pulses`provided in accordance with the operating speed of the rolling mill ittor the movement of the strip 16. These latter pulses provide ameasurement of the stri-p movement along the pass line through therolling mill 1). When the counter indicates that the proper stripmovement after the screw motor has stopped its correcting motion hasbeen provided to allow all of the strip thickness corrections that aremade to reach the thickness gauge 2t), the pulse counter device 38 sendsan output signal to reset the timing circuits through their respectivecontrol memory devices for another jogging operation if the stripthickness error has not been removed. Thusly, the screw motor 18 isjogged for a given time corresponding to the magnitude and direction ofthe thickness error and is then allowed to remain inactive until thecorrective results of this jogging movement have been measured. If thescrew correction movement provided in this manner is not sutlicient anda thickness error is still present, a subsequent jogging operation isinitiated and this is repeatedly done until the strip thickness err-oris removed. it should be readily understandable that any desired numberof signal magnitude sensing devices can be provided, although for thepurpose of illustration only three such devices have been shown. fitshould be further noted that the screw -rnotor 18 is operative in aconstant voltage screw control circuit arrangement. The motor controlapparatus of the present invention is equally operative with a variablevoltage screw control type or" apparatus or on a motor operated r'ieldrheostat arrangement.

Although the present invention has been described with a certain degreeof particularity, it should be understood that the present disclosurehas been made only by way of example and that numerous changes in thedetails of construction and the combination and arrangement of parts maybe resorted to Without departing from the scope and spirit of thepresent invention.

I claim as my invention:

1. In control apparatus for controlling the operation of a machinedevice in accordance with an operation error signal, the combination ofa first signal sensing device responsive to a first predetermined valueof said error signal, a second signal sensing device responsive to asecond predetermined value of said error signal, a first control periodproviding device operative with said first signal sensing device forproviding a first control period having a first time duration when saidfirst signal sensing device responds to a first predetermined value ofsaid error signal, a second control period providing device operativewith said second signal sensing device for providing a second con-trolperiod having a second time duration greater than said first time periodwhen said second signal sensing device responds to a secondpredetermined value of said error signal greater than said firstpredetermined value, a condition sensing device operative with saidmachine device for providing a control signal in accordance with anoperating condition of said machine device, and a machine devicecontrolling member operative with said machine device to correct saiderror signal, with said machine device controlling member beingresponsive to one of said first and second control periods andadditionally responsive to said control signal for controlling thecorrection of said error signal.

2. In motor control apparatus operative with a motor having an armatureand responsive to an operation error signal for determining theoperation of said motor, the combination of a first signal sensingdevice responsive to a first predetermined value of said error signal, asecond signal sensing device responsive to a second predetermined valueof said error signal, a first control signal providing device operativewith said first signal sensing device for providing a first controlsignal having a first time control period in accordance with said firstsignal sensing device responding to a first predetermined value of saiderror signal, a second control signal providing device operative withsaid second signal sensing device for providing a second control signalhaving a second time control period greater than said first time periodand in accordance with said second signal sensing device responding to asecond predetermined value of said error signal greater than said firstpredetermined value, motor operation sensing means operative with saidmotor for providing a third control signal in accordance with apredetermined operating condition of said motor armature, with one ofsaid first and second control signal providing devices being responsiveto said third control signal for controlling the provision of a controlsignal by said one signal providing device,

and a control member responsive to the latter control signal forcorrecting the operation error of said motor.

3. In strip thickness control apparatus, the combination of a stripthickness sensing device for providing an error signal in accordancewith the error difference between the actual strip thickness and apredetermined desired thickness, first control signal means respondingto a first predetermined value of said error signal for providing afirst control signal having a first predetermined time control period,second control signal means responding to a second predetermined valueof said error signal greater than said first predetermined value forproviding a second control signal having a second predetermined timecontrol period greater than said first time control period, stripmovement sensing means operative with the strip for providing a thirdcontrol signal in accordance with the movement of said strip, and stripthickness controlling means responsive to one of said first and secondcontrol signals and operative with said strip to provide a correctionfor said error difference at time intervals determined by said thirdcontrol signal.

4. In strip thickness control apparatus, the combination of a stripthickness sensing device for providing an error signal in accordancewith the error difference between the actual strip thickness and apredetermined desired thickness, first control signal means respondingto a first predetermined value of said error signal for providing afirst control signal having a first predetermined time control period,second control signal means responding to a second predetermined valueof said error signal greater than said first predetermined value forproviding a second control signal having a second predetermined timecontrol period greater than said first time control period, thirdcontrol signal means responding to the polarity of said error signal forproviding a third control signal when said error signal is less than apredetermined reference value and for providing a .fourth control signalwhen said error signal is greater than said reference value, stripmovement sensing means operative with the strip for providing a fifthcontrol signal in accordance withthe movement of said strip, and stripthickness controlling means responsive to one of said first and secondcontrol signals and further responsive to one of said third and fourthcontrol signals to correct said error difference in a direction tosubstantially eliminate the strip thickness error, with the schedule ofthe error correction by said strip thickness controlling means beingdetermined by said fifth control signal.

References Cited in the file of this patent UNITED STATES PATENTS1,969,536 Winne Aug. 7, 1934 2,664,557 Sargrove Dec. 29, 1953 2,708,254Macaulay et al. May 10, 1955 2,897,638 Maker Aug. 4, 1959 2,933,626Giboney et al. Apr. 19, 1960

1. IN CONTROL APPARATUS FOR CONTROLLING THE OPERATION OF A MACHINEDEVICE IN ACCORDANCE WITH AN OPERATION ERROR SIGNAL, THE COMBINATION OFA FIRST SIGNAL SENSING DEVICE RESPONSIVE TO A FIRST PREDETERMINED VALUEOF SAID ERROR SIGNAL, A SECOND SIGNAL SENSING DEVICE RESPONSIVE TO ASECOND PREDETERMINED VALUE OF SAID ERROR SIGNAL, A FIRST CONTROL PERIODPROVIDING DEVICE OPERATIVE WITH SAID FIRST SIGNAL SENSING DEVICE FORPROVIDING A FIRST CONTROL PERIOD HAVING A FIRST TIME DURATION WHEN SAIDFIRST SIGNAL SENSING DEVICE RESPONDS TO A FIRST PREDETERMINED VALUE OFSAID ERROR SIGNAL, A SECOND CONTROL PERIOD PROVIDING DEVICE OPERATIVEWITH SAID SECOND SIGNAL SENSING DEVICE FOR PROVIDING A SECOND CONTROLPERIOD HAVING A SECOND TIME DURATION GREATER THAN SAID FIRST TIME PERIODWHEN SAID SECOND SIGNAL SENSING DEVICE RESPONDS TO A SECONDPREDETERMINED VALUE OF SAID ERROR SIGNAL GREATER THAN SAID FIRSTPREDETERMINED VALUE, A CONDITION SENSING DEVICE OPERATIVE WITH SAIDMACHINE DEVICE FOR PROVIDING A CONTROL SIGNAL IN ACCORDANCE WITH ANOPERATING CONDITION OF SAID MACHINE DEVICE, AND A MACHINE DEVICECONTROLLING MEMBER OPERATIVE WITH SAID MACHINE DEVICE TO CORRECT SAIDERROR SIGNAL, WITH SAID MACHINE DEVICE CONTROLLING MEMBER BEINGRESPONSIVE TO ONE OF SAID FIRST AND SECOND CONTROL PERIODS ANDADDITIONALLY RESPONSIVE TO SAID CONTROL SIGNAL FOR CONTROLLING THECORRECTION OF SAID ERROR SIGNAL.